Solar power concentrating system

ABSTRACT

An outer side of a receiver is covered with a housing, so that the receiver is not exposed to the open air and no heat of the receiver is taken by winds, to improve thermal efficiency. Although the outer side of the receiver is covered with the housing, a lower side thereof has an opening, so that sunlight reflected by heliostats is introduced through the opening to the inside of the receiver and is surely received by an inner face of the receiver.

TECHNICAL FIELD

The present invention relates to a solar power concentrating system.

BACKGROUND TECHNOLOGY

A known solar power concentrating system arranges a receiver at the topof a tower installed on the ground, and on the ground around the tower,sets a plurality of heliostats that follow the sun. The heliostatsfollow the sun and reflect sunlight toward the stationary receiver. Thesunlight reflected by the plurality of heliostats concentrates in thereceiver to make the receiver high temperature. Inside the receiver,there is a path to pass a heating fluid (for example, molten salt).Passed through the inside of the receiver, the heating fluid becomeshigh temperature. The high-temperature heating fluid is circulatedthrough a place that needs heat (for example, a steam generator). Inthis way, the heating fluid transfers the heat of the receiver. Arelated document is, for example, U.S. Pat. No. 4,227,513.

SUMMARY OF INVENTION

According to the related art, the receiver is exposed to the open air atthe tall position, and therefore, winds take heat from the receiver. Inaddition, the high-temperature receiver radiates heat, to deterioratethermal efficiency.

In consideration of the related art, the present invention provides asolar concentrating system capable of improving thermal efficiency.

Means to Solve the Problems

According to an aspect of the present invention, the solar concentratingsystem has a receiver installed at a predetermined height and heliostatsarranged on the ground around the receiver, to reflect sunlight towardthe receiver. The receiver has an inverted container shape having at alower side thereof an opening to introduce sunlight. A housing isarranged on an outer side of the receiver, surrounds the receiver exceptthe opening, and defines a space for a heating fluid defined between thehousing and the receiver

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a general perspective view illustrating a solar concentratingsystem according to a first embodiment of the present invention

FIG. 2 is a sectional view illustrating the solar concentrating system

FIG. 3 is a sectional view illustrating a receiver

FIG. 4 is a sectional view illustrating a receiver according to a secondembodiment of the present invention

FIG. 5 is a sectional view illustrating a receiver according to a thirdembodiment of the present invention

MODE OF IMPLEMENTING INVENTION First Embodiment

FIGS. 1 to 3 are views illustrating the first embodiment of the presentinvention. At the center of a solar concentrating system according tothe present embodiment, four supports 1 having a predetermined height(about 10 m) are uprightly arranged. Around the supports 1, there are aplurality of heliostats 2 to follow the sun T and reflect sunlight Ltoward a single target position P.

The tops of the four supports 1 support a stationary receiver 3. Thereceiver 3 has an inverted container shape (inverted pot shape) havingan opening 4 at a lower side thereof and a predetermined inner space.The receiver 3 is generally made of black carbon material and an innerface thereof is covered with a silicon carbide (SiC) film. Accordingly,the color of the inner face of the receiver 3 is black to realize a veryhigh absorptance for the sunlight L. Nearly at the center of the opening4 of the receiver 3, the virtual target P of the heliostats 2 ispositioned.

Formed around the receiver 3 is a cylindrical housing 5 having a topface. The housing 5 is made of metal and has an inner face provided witha mirror coating 6. The housing 5 and receiver 3 are connected to eachother at lower parts thereof and a space S is defined between them topass air A serving as a heating fluid.

At the center of the top face of the housing 5, a cylindrical smoke vent7 is formed. A lower end of the smoke vent 7 passes through the top ofthe receiver 3 to make the inside of the receiver 3 and the outside ofthe housing 5 communicate with each other. The diameter of the smokevent 7 is small to discharge smoke created inside the receiver 3 to theoutside little by little and not to discharge a large amount of air fromthe inside of the receiver 3 to the outside.

At a lower part of a side face of the housing 5, an inlet 8 for the airA is formed. An outlet 9 is formed at a position opposite to the inlet8.

To the inside of the receiver 3 having the above-mentioned structure,the sunlight L reflected by the heliostats 2 is introduced through theopening 4. The sunlight L is once concentrated at the target P and isdiffused to hit the inner face of the receiver 3. The inner face of thereceiver 3 is black to realize a high absorptance for the sunlight L,and therefore, the receiver 3 becomes high temperature. Even if thereceiver 3 becomes high temperature, the receiver 3 is made of solidcarbon material with the inner face coated with the silicon carbidefilm, and therefore, the receiver 3 has excellent thermal resistance notto break by heat.

The inner face of the receiver 3 may partly reflect the sunlight L.However, the diameter of the opening 4 of the receiver 3 is smaller thanthe diameter of the inner space thereof and a solid angle from eachincident point on the inner face to the opening 4 is small, so that thesunlight L hardly escapes outside. Namely, components of the sunlight Lscattered by the inner face of the receiver 3 mostly advance toward thedepth of the inner space to hit the inner face and be absorbed thereby.When the inside of the receiver 3 becomes high temperature, smoke maysometimes be produced in the receiver 3. The smoke is discharged throughthe smoke vent 7, so that no smoke will present to block the sunlight L,and therefore, the sunlight L surely reaches the inner face of thereceiver 3.

On an outer side of the receiver 3 that is at high temperature due toabsorption of the sunlight L, there is the space S in which the air Aserving as a heating medium flows. The air A comes in contact with theouter face of the receiver 3, is heated thereby, and circulates heat toa place that needs the heat.

According to the present embodiment, the outer side of the receiver 3 iscovered with the housing 5 so that the receiver 3 is not exposed to theopen air. This prevents heat of the receiver 3 from being taken by windsand improves thermal efficiency.

Although the outer side of the receiver 3 is covered with the housing 5,the opening 4 is formed at the lower side of the receiver 3, andtherefore, the sunlight L reflected by the heliostats 2 is introducedthrough the opening 4 to the inside of the receiver 3 and is surelyabsorbed by the inner face of the receiver 3.

The receiver 3 has an inverted container shape having the opening 4 atthe lower side thereof, and therefore, air A heated in the receiver 3stays inside the receiver 3 to maintain the receiver 3 at hightemperature. The heated air A tends to move upward, and therefore, ifthe opening 4 is formed at an upper side of the receiver 3, the heatedair A will cause an upward flow to escape from the receiver 3, and inplace thereof, cold air A will enter the receiver 3 to cool the receiver3 and deteriorate thermal efficiency. This will not happen according tothe present embodiment.

The inner face of the housing 5 is provided with the mirror coating 6 toform a reflector. As a result, high-temperature radiation from thereceiver 3 is reflected toward the receiver 3, thereby a heat radiationout from the receiver 3 is effectively suppressed.

According to the present embodiment, only the inner face of the receiver3 is provided with a silicon carbide (SiC) film. Instead, the receiver 3may entirely be covered with a silicon carbide (SiC) film.

To increase a contact area with air A in the space S, the outer face ofthe receiver 3 may be made undulated.

Second Embodiment

FIG. 4 is a view illustrating the second embodiment of the presentinvention. The present embodiment has components that are similar tothose of the first embodiment. The similar components are representedwith common reference marks to omit a repetition of explanation.

According to the present embodiment, the shape of a receiver 10 iscylindrical having a top face, like a housing 5. The receiver 10 that iscylindrical and has the top face is easy to form. The diameter of anopening 11 is larger than that of the preceding embodiment, andtherefore, components of sunlight L going outside due to reflection mayslightly increase. The larger opening 11, however, is capable ofreceiving sunlight L even if an accuracy of collecting sunlight fromheliostats is low. The height of the cylindrical shape of the receiver10 may be increased to decrease a solid angle from an incident point onan inner face of the receiver 10 to the opening 11, so that sunlight Lscattered by the inner face may advance toward the depth of an innerspace of the receiver 10, to improve a sunlight absorbing efficiency.

Third Embodiment

FIG. 5 is a view illustrating the third embodiment of the presentinvention. The present embodiment has components that are similar tothose of the above-mentioned embodiments. The similar components arerepresented with common reference marks to omit a repetition ofexplanation.

According to the present embodiment, a receiver 12 is integrally formedwith a housing 13. The housing 13 is divided into an upper member 14 anda lower member 15 that are welded together with peripheral flanges 14 fand 15 f. The receiver 12 has an inverted container shape with a narrowopening 16, like that of the first embodiment. The receiver 12 isintegrally and continuously formed from a bottom face of the lowermember 15 from the same material. A smoke vent 7 is formed from theupper member 14 and is passed through and welded to an upper part of thereceiver 12.

According to the present embodiment, water W is used as a heating fluid.The water W is supplied into an inlet 8 and is passed through a space S,thus the water W comes in contact with the receiver 12 and is heatedthereby and hot water W is taken out of an outlet 9.

According to the present embodiment, the receiver 12 is integrallyformed as part of the housing 13, and therefore, no gap is presentbetween them. This is appropriate for passing a liquid such as water Was a heating fluid.

According to the present embodiment, water W is used as a heating fluid.Instead of the water W, a liquid such as oil is employable. An innerface of the receiver 12 may be coated with a heat-resistant blackcoating.

Effect of Invention

According to the present invention, the outer side of the receiver iscovered with the housing, and therefore, the receiver is not exposed tothe open air. This prevents heat of the receiver from being taken bywinds and improves thermal efficiency. Although the outer side of thereceiver is covered with the housing, the opening is formed at a lowerside of the receiver. Accordingly, sunlight reflected by the heliostatsis introduced through the opening to the inside of the receiver and issurely received by the inner face of the receiver. Between the receiverand the housing, the space for a heating fluid is formed so that theheating fluid introduced into the space comes in contact with the outerface of the receiver and is heated thereby. The receiver has an invertedcontainer shape with the opening formed at the lower side thereof, sothat air heated in the receiver stays therein to maintain the receiverat high temperature.

According to another aspect of the present invention, the diameter ofthe opening of the receiver is smaller than the diameter of the insideof the receiver to reduce a solid angle. Accordingly, sunlightintroduced into the receiver and reflected by the inner face of thereceiver will rarely escape outside through the opening.

The receiver is made of solid silicon carbide, or solid silicon carbideentirely covered with a silicon carbide film. The inner face of thereceiver is black due to the silicon carbide film, to improve a sunlightabsorptance. At least the surface of the receiver is formed with asilicon carbide film, to provide excellent heat resistance.

Further, the inner face of the housing is provided with a mirrorcoating. If the heating fluid is a transparent gas such as air, themirror coating reflects radiation from the high-temperature receiverback to the receiver, thereby preventing heat radiation from thereceiver.

Also, the receiver is integrally formed from part of the housing, toproduce no gap between them. This is appropriate when the heating fluidis a liquid.

UNITED STATES DESIGNATION

In connection with United States designation, this international patentapplication claims the benefit of priority under 35 U.S.C. 119(a) toJapanese Patent Application No. 2009-99980 filed on Apr. 16, 2009, theentire content of which is incorporated by reference herein.

1. A solar concentrating system having a receiver installed at apredetermined height and heliostats arranged on the ground around thereceiver, the heliostats reflecting sunlight toward the receiver,wherein: the receiver has an inverted container shape having an openingat a lower side thereof to introduce sunlight; a housing is arranged onan outer side of the receiver and surrounds the receiver except theopening; and a space for a heating fluid is defined by the housing andthe receiver.
 2. The solar concentrating system according to claim 1,wherein the diameter of the opening of the receiver is smaller than thatof the inside of the receiver.
 3. The solar concentrating systemaccording to claim 1, wherein the receiver is made of solid siliconcarbide, or solid carbon material entirely covered with a siliconcarbide film.
 4. The solar concentrating system according to claim 1,wherein an inner face of the housing is provided with a mirror coating.5. The solar concentrating system according to claim 1, wherein thereceiver is made from the same material as the housing so that thereceiver is continuous and integral with the housing.
 6. The solarconcentrating system according to claim 2, wherein the receiver is madeof solid silicon carbide, or solid carbon material entirely covered witha silicon carbide film.
 7. The solar concentrating system according toclaim 2, wherein an inner face of the housing is provided with a mirrorcoating.
 8. The solar concentrating system according to claim 3, whereinan inner face of the housing is provided with a mirror coating.
 9. Thesolar concentrating system according to claim 2, wherein the receiver ismade from the same material as the housing so that the receiver iscontinuous and integral with the housing.
 10. The solar concentratingsystem according to claim 3, wherein the receiver is made from the samematerial as the housing so that the receiver is continuous and integralwith the housing.
 11. The solar concentrating system according to claim4, wherein the receiver is made from the same material as the housing sothat the receiver is continuous and integral with the housing.